Add auto-generated documentation

[wing328]

We've add capabilities to generate documentation files (markdown) for API and model files in the Perl code generator: #2320, #2343

If anyone has cycle to add the documentation to the following languages, please reply to let us know:

• Android (add pom.xml based on build.gradle for android api client( using the v… #2773)
• Bash
• C++
• C# ([CSharp] Add auto-generated CSharp documentation in Markdown  #2595)
• Clojure
• Dart ([Dart] add auto-generated documentation #4291)
• Elixir
• Flash
• Go (issue#2359: added README document generation for Go #2608)
• Groovy
• Javascript ([JavaScript] Add auto-generated documentation in Markdown to JS client #2391)
• Java ([Java] Add auto-generated documentation in Markdown to Java clients #2435)
• ObjC ([ObjC] Add auto-generated documentation (markdown) to ObjC API client #2482)
• Perl ([Perl] Add auto-generated Perl documentation in Markdown #2320, [Perl] fix link to File type in documentation, add .gitignore #2343)
• PHP ([PHP] Add documentation (markdown) to APIs and models #2388)
• Python ([Python] automatically generate documentation (markdown) for Python API client #2472)
• Ruby ([Ruby] Add auto-generated documentation in Markdown to Ruby client #2344)
• Swift
• Scala
• TypeScript